Technology Demonstration

A technology demonstration called Mars Cube One (MarCO) will be the first deep space use of miniature, modular "CubeSat" spacecraft design. The pair of briefcase-size spacecraft -- MarCO-A and B -- will launch on the same rocket as InSight and carry out a number of risky communication and navigation flight experiments. If successful, the twins, MarCO-A and MarCO-B, will fly separately towards Mars and potentially pass the planet at about 2,175 miles (3,500 kilometers) away just as InSight is landing. One could potentially receive transmissions from InSight and relay status information to Earth about the lander's descent and touchdown.

All previous CubeSats have orbited the Earth. MarCO is the first attempt to go to another planet. By verifying that the technologies for interplanetary missions are feasible and can be developed on a short timeline, this test mission could lead to many other SmallSat applications for exploring our solar system. Some could provide similar support functions as "carry your own" relay providers. Others could have primary scientific research functions of their own, such as radio transmissions through planetary atmospheres, imaging with small cameras, observations with other miniaturized instruments, or in-place measurements of space environments.

The success of the InSight mission does not depend on MarCO's performance. NASA's Mars Reconnaissance Orbiter (MRO) and large radio telescopes on Earth are also expected to receive transmissions from InSight during descent and landing. MRO will hold that data for more than an hour while circling Mars before transmitting it to Earth. The radio telescopes will only be able to listen for “aliveness.” However, should a MarCO CubeSat make it all the way to Mars, each has the capability to relay a substantive amount of data almost immediately, transmitting status information on an 8.7-minute, speed-of-light trip to Earth across about 97.5 million miles (157 million kilometers) between the two planets.

JPL engineer Joel Steinkraus works with one of the MarCO CubeSats during an outdoor test of its solar arrays.

JPL engineer Joel Steinkraus works with one of the MarCO CubeSats during an outdoor test of its solar arrays.

The reason for flying two identical MarCO spacecraft is redundancy in case either one does not operate as planned.

Mars Cube One Illustration

CubeSats are a class of spacecraft based on a standardized small size and modular use of off-the-shelf technologies. Many have been made by university students, and hundreds have been launched into Earth orbit using extra payload mass available on launches of larger spacecraft.

The basic CubeSat unit is a box roughly 4 inches (10 centimeters) square. Larger CubeSats are multiples of that unit. MarCO's design is a six-unit CubeSat. Each of the two spacecraft has a stowed size of about 14.4 inches (36.6 centimeters) by 9.5 inches (24.3 centimeters) by 4.6 inches (11.8 centimeters).

The spring-loaded CubeSat deployment system for MarCO is on the aft bulkhead carrier of the Centaur upper stage of InSight's Atlas V launch vehicle. That is near the base of the Centaur, not inside the fairing that encloses the main spacecraft. At launch and until the Centaur upper stage separates from the first stage of the Atlas V, the aft bulkhead carrier is sheltered within an inter-stage adaptor between the launch vehicle and the second, or upper, stages.

After the Centaur upper stage has released the InSight spacecraft on course toward Mars, it will do a short roll, then release MarCO-A, roll 180 degrees further and release MarCO-B.

Illustration of one of the twin MarCO spacecraft with some key components labeled.

Illustration of one of the twin MarCO spacecraft with some key components labeled. Front cover is left out to show some internal components. Antennas and solar arrays are in deployed configuration. Download image

After Separation

If all goes according to plan, within about 10 minutes after separation from the Centaur, each MarCO will begin to deploy its solar panels. Each MarCO generates electric power with a pair of photovoltaic panels, and each panel has an area of about 12 inches by 12 inches (30 centimeters by 30 centimeters). Combined, these panels can provide each spacecraft about 35 watts when near Earth and 17 watts when near Mars. The power system also will use rechargeable lithium-ion battery cells, crucial for operations when spacecraft orientation for communication prevents the solar arrays from facing the Sun.

After the solar arrays are deployed, the MarCO control team will acquire radio contact with each CubeSat, one at a time, via NASA's Deep Space Network. Early tasks will be to establish that the spacecraft are healthy, stable and commandable.

During the flight to Mars, the MarCO twins will each attempt to deploy a high-gain X-band antenna that is a flat "reflectarray" panel engineered to direct radio waves the way a parabolic dish antenna does. This will allow MarCO to transmit data to Earth from as far away as Mars without needing much power, if the spacecraft works as planned. Two smaller X-band antennas on each spacecraft -- one low-gain and one medium-gain -- work without needing to be deployed. These will serve for transmissions earlier in the flight and will also receive radioed commands from Earth.

The other deployed antenna is for the MarCO ultra-high frequency (UHF) radio receiver. InSight will be transmitting in UHF during its descent through the Martian atmosphere and from the surface of Mars. Both of the deployed antennas on each MarCO will be in fixed positions after deployment, with the high-gain antenna and UHF antenna facing different directions 90 degrees apart. The MarCOs will also test new technology using a softball-size radio, called "Iris." This radio provides both UHF (receive only) and X-band (receive and transmit) functions capable of immediately relaying information received over UHF, at 8 kilobits per second.

A color wide-field engineering camera on each MarCO will be used to confirm high-gain antenna deployment. The wide-field camera has a 138-degree diagonal field of view and produces images 752 by 480 pixels in resolution. Each MarCO was also designed with a color narrow-field camera with a 6.8-degree diagonal field of view pointed in the direction of the UHF antenna (the opposite direction from the high-gain antenna)(MarCO-A’s narrow-field camera was found to be inoperable prior to launch.) Both kinds of cameras can produce images 752 by 480 pixels in resolution.

The team will navigate MarCO-A and MarCO-B separately to Mars with course adjustments along the way. The first of five opportunities for MarCO trajectory correction maneuvers will come about a week after launch.

Each MarCO's attitude-control system combines a star tracker, Sun sensors, gyroscopes and three-axis reaction wheels for monitoring and adjusting orientation. Accelerating a reaction wheel rotates the spacecraft in the opposite direction from the direction the wheel is spinning.

MarCO Illustration

MarCO's propulsion system uses compressed R236FA gas, a common propellant in fire extinguishers. Each MarCO has eight thrusters that can release this cold-gas propellant in different directions from a single, shared tank. The thrusters will operate for trajectory adjustments and for desaturating the reaction wheels. MarCO is pioneering CubeSat use of propellant for desaturating attitude-control reaction wheels; Earth-orbiting CubeSats typically control attitude with electromagnet devices that “push” against Earth’s magnetic field, an option not available to MarCO in deep space.

The "cruise" period of flying from Earth to Mars will be used to complete the communication and navigation technology demonstration objectives. They will also include checkouts of MarCO's temperatures, power levels and other onboard subsystems. Each MarCO carries heaters, multiple temperature sensors, thermal blanketing and two radiators for thermal control.

If all goes well, on Nov. 26, 2018, MarCO-A and MarCO-B could be flying past Mars during the critical minutes when InSight enters the Martian atmosphere, descends toward the surface and touches down. Each MarCO will maintain an orientation with the UHF antenna pointed down toward InSight as it lands on Mars, and the high-gain X-band antenna pointed back toward Earth. In this orientation, the solar panels will not face the Sun, so MarCO will be operating on battery power. InSight will be transmitting its status information at 8 kilobits per second over UHF. Each MarCO will attempt to receive that data stream, format it and relay it Earthward in near-real-time to NASA’s Deep Space Network. Since MarCO adds formatting information, as well as a small amount of spacecraft information, to the datastream, the delay is expected to increase as more data are sent from InSight. The delay, however, is not expected to be more than a few minutes. Earth will be oriented so that the information relayed via MarCO will go to the Madrid, Spain, station of the Deep Space Network, from which it will be routed to the InSight mission operations team.

NASA's Jet Propulsion Laboratory, Pasadena, California, which manages both InSight and MarCO for NASA, built the two MarCO spacecraft in JPL's CubeSat assembly clean room. At JPL, Joel Krajewski is MarCO's project manager and Andrew Klesh is MarCO's project engineer.

Technology suppliers for MarCO include: Blue Canyon Technologies of Boulder, Colorado, for the attitude-control system; VACCO Industries of South El Monte, California, for the cold-gas thrusters; AstroDev of Ann Arbor, Michigan, for electronics; MMA Design LLC, also of Boulder, for solar arrays; and Tyvak Nano-Satellite Systems Inc., a Terran Orbital Company in San Luis Obispo, California, for the CubeSat dispenser system. United Launch Alliance, Centennial, Colorado, is providing the Atlas V and launch services.

Mars Cube One Illustration

MarCO will relay data from InSight to Earth during InSight's descent through Mars' atmosphere and touchdown on the surface. NASA's Mars Reconnaissance Orbiter will also receive these data from InSight.
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